Technology:Phytoremediation
- Demonstration area is approximately 2,034 m2 and contains 156 viable poplars
- Two-year-old hybrid poplars were planted 5 to 6 ft in Spring 1996; surficial drainage was installed to remove precipitation quickly and allowed trees to reach groundwater
- New trees were planted in October 1998 to increase the phytoremediation area and assess the usefulness of native species for phytoremediation

Results:Sampling was performed for groundwater; sap flow monitoring; tree transpiration gas and condensate sampling; and exposure pathway assessments
Groundwater level data indicated that hydraulic influence is occurring, with the trees currently removing 1,091 gpd and at the end of 30 years expected to remove 1,999 gpd
Contaminated plume has not migrated off-site during the growing seasons
Contaminant uptake is minimal at this time but expected to improve as the trees mature

Cost Factors:Capital costs of $80/tree including $5,000 for initial site preparation, additional $80,000 for UXO clearance of soil during planting; O&M costs: $30,000

Description:Aberdeen Proving Grounds is located at the tip of the Gunpowder Neck Peninsula in Edgewood Maryland. At APG, the Army practiced open trench (toxic pits) open burning/detonation of munitions containing chemical agents and dunnage from the 1940s to the 1970s. Large quantities of decontaminating agents containing solvents were used during the operation, and the surficial groundwater table was contaminated with solvents (1,1,2,2-TCA, TCE, DCE) at levels up to 260 ppm. A demonstration of phytoremediation to clean up shallow groundwater was performed at the site was performed by the U.S. Air Force (USAF) as part of the Department of Defense's (DOD's) Environmental Security Technology Certification Program (ESTCP), and the SITE Program.

At the APG site, a process called deep rooting was used to achieve hydraulic influence. Hybrid poplar trees were planted in the spring of 1996 at five to six feet bgs to maximize groundwater uptake. The field demonstration and evaluation will be for a five year period. The U.S. Geological Survey has estimated that hydraulic influence will occur when 7,000 gallons of water per day are removed from the site. The latest field data indicates that hydraulic influence is occurring. Current tree uptake is 1,091 gpd and is expected to increase to 1,999 gpd at the end of 30 years. Contaminant uptake is minimal at this time but is expected to improve as the trees mature. Groundwater sampling indicates that the contaminated plume has not migrated off-site during the growing season and sampling data showed non-detectable emissions from transpiration gas. There are several on-going studies to determine if deleterious compounds retained in the leaves and soil could pose risks to environmental receptors. Cost for site preparation included additional costs for UXO clearance, for a total of $80/tree, with O&M costs of $30,000 per year.